Circuit arrangement for generating a sawtooth-shaped current in a coil



J ly 12, 19 B. w. VAN INGEN SCHENAU 5,

CIRCUIT ARRANGEMENT FOR GENERATING A SAWTOOTH-SHAPED CURRENT IN A COILFiled March 26, 1948 AGIF/VT Patented July 12, 1949 UNI'IED STAT COILBernardus Willem van Ingen Schenau, Eindhoven,

Netherlands, assignor to Hartford National Bank and Trust Company,Hartford,

Conn, as trustee Application March 26, 1948, Serial No. 17,246 In theNetherlands April 21, 1947 3 Claims.

The invention relates to a circuit-arrangement for producing in a coil asawtooth-shaped current with the aid of a discharge tube to which asawtooth-shaped voltage is supplied, wherein the anode circuit of thistube includes the primary Winding of a transformer and the coil isconnected to a secondary winding of this transformer, a diode beingconnected into the said circuit so as to be conductive during the strokeof the sawtooth-shaped current.

In the known circuit-arrangements of this kind the cathode of the diode,usually referred to as efiiciency-diode, is connected to that point ofthe circuit at which during the fly-back of the current occurs in theanode circuit the highpulse-voltage of, for example, 4000 volts orupwards, the said point being that end of the primary winding of thetransformer which is located near the anode of the discharge tube.

The fiy-back time of the sawtooth-current is determined by the firsthalf-period of the natural oscillation of the circuit formed by theself-induction of the transformer and the capacities of the latter andof the tube and the wiring system and mostly this time should be asshort as possible. To that end use must be madeof a winding having onlylittle capacity and, moreover, the supply of the cathode of theemciencydiode must be effected in a substantially capacity-free manner,which, on account of the fact that, in addition, this supply must berealised in an insulated manner with respect to the high pulse-shapedvoltages produced, entails additional difiiculties.

The circuit-arrangement according to the invention obviates thesedisadvantages and exhibits the feature that the cathode of the diode isconnected to that end of the primary transformer Winding which is remotefrom the anode of the discharge tube, and that a second secondarytransformer winding is included in the anode circuit of the diode.

With this circuit-arrangement the cathode of the diode is consequentlyconnected to a point at which occurs only a comparatively lowdirectvoltage, viz. the positive voltage of the anodevoltage source ofthe discharge tube, so that the supply of this cathode does not entailadditional disadvantages.

The invention will be explained more fully with reference to theaccompanying drawing in which Fig. 1 represents, by way of example, acircuit-arrangement according to the invention. Fig. 2 represents, byway of example, a transformer for use in Fig. 1.

Input terminals I and 2 of the control-grid circuit of a discharge tube3 in Fig. 1 have supplied to them a sawtooth-shaped voltage which istaken, for example, from a blocking oscillator. For example, in acircuit-arrangement for a television-receiver this oscillator may besynchronized by the supply of line synchronizing pulses. The anodecircuit of the tube includes the primary winding 4 of a transformer 5 tothe secondary winding 6 of which are connected defiector coils idestined to bring about, for example, the horizontal deflection of thecathode ray beam of a cathode ray tube.

The transformer 5 comprises another secondary winding 8 which isincluded in the anode circuit of an efl'iciency-diode 9 the cathode H)of which is connected to the positive terminal H.

of an anode voltage supply 12, the cathode Ill being consequentlyconnected at the same time to that end of the primary transformerwinding, 4 which is remote from the anode of the tube 3..

It will be evident that during the stroke of the sawtooth-shaped currentin the coils I, when consequently the anode current of the dischargetube 3 increases linearly and, due to the selfinduction of the Winding4, the anode voltage has decreased by a certain amount, the voltageacross the winding 8 has increased by a certain amount, so that theefficiency-diode is conductive and consequently there occurs an effectsimiilar to that occurring in the known circuitarrangements.

It may be noted that, for obtaining a circuitarrangement with which alow voltage is applied to the cathode of the diode 9, it is notnecessary to use a transformer comprising three windings.

Alternatively, the deflector coils I may be coupled directly to thewinding 8, in which event, however, high voltages are set up across thecoils 1. If, on the other hand, we wanted to avoid this disadvantage bymeans of another transformation ratio between the windings 4 and 8, thediode 9 must have a low internal resistance, which can be realised withgreat difliculty only.

According to one advantageous embodiment of a circuit-arrangementaccording to the invention, the transformer is constructed in suchmanner that no coupling or substantially no coupling exists between thestray self-induction of the primary winding 4 with respect to the secondsecondary winding 8, on the one hand, and that of the latter windingwith respect to the other secondary winding 6 to which the deflectorcoils are connected, on the other hand, for it has been found that dueto the existence of coupling between these stray self-inductions in thewindings 4 and 8 a line raster free of disturbances may now be describedif the coupling between the stray self-inductions of the windings.

4 with respect to the winding 8 and of the latter Winding with respectto the winding 6 is eliminated.

Fig. 2 represents, by way of example, a trans-;-

former for use in a circuit-arrangement accordin to the invention. Acylindrical core l3 of magnetic material has provided onit a secondary Iwinding I4 which extends for a distance-smaller 1 than the length of thecore. The coils 7 of Fig.1 are connected to this winding. Outsidethereof is provided the secondary winding I5, which is includedin thediode circuit and which extends over a distance exceeding the length ofthe winding [4. The winding i is surrounded by the primary winding l6.With such a construction'of the transformer coupling between the strayself-'- induction of the winding With respect to the winding l6 and thestray self-induction of the winding M with respect to the winding I 5may substantiallycompletely be avoided.

What I claim is:

1. An electrical circuit arrangement forproducing a saw-toothshapedcurrent in the deflection coil of a cathode ray tube, comprising an'electron discharge tube having'a cathode, a control grid and an anode,means to apply a sawtooth shaped voltage to the cathode and controlgrid, a transformer comprising a high impedance primary winding havinthe ends thereof spaced apart and having one end thereof connected tothe anode, a low impedance secondary winding and a high impedancetertiary winding, a source of potential having the negative pole thereofconnected to the cathode and having the positive pole thereof connectedto the other end of said primary winding, means to couple the secondarywinding to the said deflection coil, anda diode element having a cathodeconnected to the end'of the primary vwnding remote from the said anodeand having an anode connected to saidtertiary winding.

2. An electrical circuit arrangement for producing a saw-tooth shapedcurrent in the deflection coil of a cathode ray tube, comprising anelectron discharge tube-having a cathode,.a control grid and an anode,means to app y a wtooth shaped voltage to the cathode and control grid,a transformer comprising a high impedance primary windinghaving" the;ends thereof spaced apart and havin one end'therecf connected to theanode, a low impedance secondary winding and a high impedance tertiarywinding having the-ends thereof positioned adjacent the respective endsof the primary winding, a source of potential having the'negative polethereof connected to the cathode and having the positive polethereof-connected to the other end of said primary'winding; means tocouple the secondary winding'to the. said deflection coil, and a diodeelement having a cathode connected to the end of thezprimarywindingremote from the said anode and having an anode connected to the end ofthe tertiary Winding remote from the anode end of the primary winding.

3. An electrical circuit arrangement for producinga'saw-tooth shapedcurrent in the deflectioncoilof a cathode ray tube, comprising anelectron discharge tube having a cathode, a control grid and an anode,means-to apply a sawtooth shaped-voltage tothe cathode and control grid,a transformer comprising a" core member, a low impedance secondarywinding wound on said core, a high impedance tertiary-Winding super--imposed on said secondary windin and a high impedance primary windingsuperimposed on'said secondary winding, having the-ends thereof spaced'apart and-having one end thereof connected to the anode, a sourceof'potentialhaving' the negative pole-thereof connected to the cathodeand having=thepositive pole thereof connected-to the otherend of saidprimary winding, means to couple'the secondary winding to the saiddeflection coil, and a diode element having a cathode connected to theend of the primary windingremote from the said anodeand having an anodeconnected to said tertiary winding.

BERNARD'US WILDEM VAN INGEN SCHENAU.

REFERENCES CITED The following, references are of record in the file ofthis patent;

UN ITED STATES PATENTS Number Name Date 2,265,620 Bahring Dec. 9, 19412,438,359 Clapp' Mar. 23, 1948 2,440,418 Tourshou Apr. 27, 19482,451,641 Torsch Oct. 19, 1948

